Lecture 21: Weather Flashcards
What does Weather give?
The conditions of the atmosphere at a specific place and time on the planet
What is the Pressure Gradient flow?
When air is heated at the equator and forms a low pressure gradient and moves towards the high pressure at the poles
What is wind speed controlled by?
The pressure gradient
What are Isobars?
Lines of constant pressures
How do Isobars affect wind speed?
If isobars are far apart this means there is low pressure and low speed
What occurs in Geostrophic flow?
When wind flows parallel to isobars due to the coriolis effect balancing the pressure gradient
What are the cells of Global air circulation from middle to end?
Hadley, Ferrel, Polar
What are Hadley cells driven by and where are they located?
Driven by pressure gradient flow and located near the equator
What are Ferrel cells driven by?
Movement of adjacent cells, they are poorly defined
What are Polar cells driven by?
Pressure gradient flow and they are located near the poles
What breaks up the air circulation patterns into 6 cells?
The coriolis effect
What is the movement of winds at high altitudes?
Winds are Geostrophic because friction reduces the Coriolis effect on pressure gradient flow
What are Ekman spirals?
When high pressure areas have CW outward spiralling winds and low pressure areas have CCW inwards spiralling winds
What are Ekman spirals in the atmosphere caused by?
Modification of pressure gradient flow by the Coriolis force
What is the Intertropical Convergence Zone (ITCZ)?
A zone of low pressure near the equator
What are Easterlies?
Persistent winds that dominate the equatorial zone
What are the Westerlies?
Persistent winds that are above high pressure zones
What are Trade winds?
Persistent wind patterns like the easterlies and westerlies
What results in the Jet stream?
The mid latitude change in altitude of the tropopause that causes a steep pressure gradient
What controls the position jet stream?
Where cold air intersects with warm air called Rossby waves where they change position
What is Weather controlled by?
Air masses
What are Air masses?
Large volumes of air that have internally consistent properties, including pressure, humidity and temperature
What are Air Masses Characterized by?
Do they form over a continent (c) or maritime regions (m), do they form in the Tropics (T) or in Polar regions (P)
What are monsoons?
Seasonal migration of pressure belts that reverses wind directions near the equator causing heavy rain
What do Sea Breezes result from?
Loca pressure gradient winds when the land heats faster than the sea causing a region of low pressure and wind blows towards the land
What do Land Breezes result from?
Land cooling faster than the sea at night causing wind to flow towards the sea
What are Mountain and Valley winds?
When warm winds are in valleys during the day and cold winds are in valleys during the night
When do Chinooks occur?
When regional atmospheric flow forces air over the mountains and it descends and brings warm air
How do Thunderstorms form?
Warm moist air masses during the day where cold fronts contact cP air
What is lightning?
Electrical discharge that occur to balance the separation between the positive top and the negative bottom of clouds
What are Tornadoes initiated by?
Spiral Updrafts with tightly rotating centers that typically rotate in the direction of the larger air mass
What do Tropical Cyclones require?
Warm moist air, condensation to supply latent heat for density lifting, the coriolis effect
